JP2564929B2 - Front and rear wheel steering vehicle rear wheel steering control device - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a rear wheel steering control device for a front and rear wheel steering vehicle, which comprises front wheel steering angle detection means and yaw rate detection means, and steers the rear wheels according to the front wheel steering angle and yaw rate detected by the both detection means. .

[Prior art]

Conventionally, as shown in, for example, Japanese Unexamined Patent Publication No. 63-207772, this type of device is used to detect the front wheel steering angle and the yaw rate when both the front wheel steering angle detecting means and the yaw rate detecting means are normal. Based on this, the target rear wheel steering angle is calculated according to the sum of the front wheel steering angle control component that increases as the front wheel steering angle increases and the yaw rate control component that increases as the yaw rate increases, and the rear wheel is set to the target rear wheel steering angle. When steering control is performed and an abnormality occurs in the yaw rate detecting means, a target rear wheel steering angle is calculated by adding a correction amount corresponding to the yaw rate control component to the front wheel steering angle control component, and the target rear wheel steering angle is calculated. The rear wheels are steered to the steering angle so that the steering stability of the vehicle can be kept good even when an abnormality occurs in the yaw rate detecting means.

[Problems to be Solved by the Invention]

However, in the above-mentioned conventional device, no countermeasure is taken when an abnormality occurs in the front wheel steering angle detecting means, and in such a case, there is a problem that the steerability of the vehicle deteriorates. The present invention has been made to address the above problems,
The purpose of the front and rear wheel steering vehicle is to ensure that the steering stability of the vehicle is kept good even when an abnormality occurs in the front wheel steering angle detection means when an abnormality occurs in the front wheel steering angle detection means. To provide a rear wheel steering control device.

[Means for Solving the Problems]

To achieve the above object, the structural features of the present invention are, as shown in FIG. 1, a rear wheel steering mechanism 1 (corresponding to the rear wheel steering mechanism B) that steers rear wheels RW, and a front wheel steering angle. Front-wheel steering angle detection means 2 for detecting (corresponding to the front-wheel steering angle sensor 41)
A yaw rate detecting means 3 for detecting a yaw rate (corresponding to the yaw rate sensor 43), a target rear wheel steering angle is determined based on the detected front wheel steering angle and the detected yaw rate, and the rear wheel steering mechanism 1 is electrically controlled. In a rear wheel steering control device for a front and rear wheel steering vehicle, which comprises an electric control device 4 (corresponding to the microcomputer 45) for steering the rear wheel RW to the target rear wheel steering angle, the electric control device 4 Abnormality detecting means 4a for detecting an abnormality of the angle detecting means 2 (step
(Corresponding to the processing of 58), and a front wheel steering angle control component that increases as the front wheel steering angle increases based on the detected front wheel steering angle and the detected yaw rate when no abnormality of the front wheel steering angle detection means 2 is detected by the abnormality detection means 4a. First target rear wheel steering angle determining means for determining the sum of the yaw rate control component increasing as the yaw rate increases as the target rear wheel steering angle
4b (corresponding to the processing of step 61), and when the abnormality detecting means 4a detects an abnormality in the front wheel steering angle detecting means 2, it corresponds to the front wheel steering angle control component with respect to the yaw rate control component based on the detected yaw rate. A second target rear wheel steering angle determining means 4c (corresponding to the process of step 63) that determines an amount including a correction amount as the target rear wheel steering angle, and a control signal corresponding to the determined target rear wheel steering angle. It is configured by the control signal output means 4d (corresponding to the processing of step 66) which outputs to the rear wheel steering mechanism 1 to control and set the rear wheels to the determined target rear wheel steering angle.

[Action]

In the present invention configured as described above, when the abnormality of the front wheel steering angle detecting means 2 is not detected by the abnormality detecting means 4a, the target rear wheel steering angle is detected by the first target rear wheel steering angle determining means 4b. Based on both the steering angle and the detected yaw rate, it is determined as the sum of the front wheel steering angle control component that increases as the front wheel steering angle increases and the yaw rate control component that increases as the yaw rate increases. On the other hand, when the abnormality of the front wheel steering angle detecting means 2 is detected by the abnormality detecting means 4a, the target rear wheel steering angle is determined by the second target rear wheel steering angle determining means 4c based on only the detected yaw rate, and the yaw rate control component is calculated. On the other hand, it is determined to be a value in which a correction amount corresponding to the front wheel steering angle control component is added. Then, by the cooperation of the control signal output means 4d and the rear wheel steering mechanism 1, the rear wheels RW are steered to the respective determined target rear wheel steering angles according to the respective states.

【The invention's effect】

As can be understood from the above description of the operation, according to the present invention, when an abnormality occurs in the front wheel steering angle detecting means 2, the detected front wheel steering angle indicating an abnormal value is not used, and only the detected yaw rate is used. Since the rear wheels RW are controlled to be steered to the target rear wheel steering angle determined by the above, the rear wheels RW will not be steered abnormally. Further, the target rear wheel steering angle in this case is the front wheel steering angle detecting means 2 and the yaw rate detecting means 3.
Is determined to be a value in which the correction corresponding to the front wheel steering angle control component when both of the detection means 2 and 3 are normal is added to the yaw rate control component when both are normal. The rear wheel steering control based on the component is supplemented by the detected yaw rate, so that even if an abnormality occurs in the front wheel steering angle detection means 2, the steering stability of the vehicle can be kept good. Specifically, the rear wheel steering control by the front wheel steering angle control component improves the turning performance of the vehicle, but even when the control by the front wheel steering angle control component cannot be performed, the vehicle is corrected by the yaw rate control component. It is possible to maintain good turning performance.

【Example】

An embodiment of the present invention will be described below with reference to the drawings.
FIG. 2 schematically shows the entire front and rear wheel steering vehicle according to the present invention. This front and rear wheel steering vehicle is an electric control device that electrically controls a front wheel steering mechanism A that steers left and right front wheels FW1 and FW2, a rear wheel steering mechanism B that steers left and right rear wheels RW1 and RW2, and a rear wheel steering mechanism B. It has C and. The front wheel steering mechanism A has a steering wheel 11. The steering wheel 11 is connected to the left and right front wheels FW1 and FW2 via the steering shaft 12, the rack and pinion mechanism 13, the relay rod 14, the left and right tie rods 15a and 15b, and the left and right knuckle arms 16a and 16b, and the turning of the handle 11 is performed. The left and right front wheels FW1 and FW2 are steered accordingly. A control valve 17 is attached to the lower part of the steering shaft 12, and the valve 17 is a hydraulic pump.
The hydraulic oil discharged by 18 and supplied through the conduit P1 is supplied to the power cylinder 21 according to the steering torque acting on the steering shaft 12.
The oil is supplied to one of the oil chambers, and the hydraulic oil from the other oil chamber of the cylinder 21 is discharged to the reservoir 22 via the conduit P2.
The power cylinder 21 drives the relay rod 14 in the axial direction in accordance with the supply and discharge of the hydraulic oil, so that the left and right front wheels FW1, FW2
It assists the steering. The rear wheel steering mechanism B has an electric motor 23, which is controlled by an electric control device C to drive the steering shaft 24 in rotation. The steering shaft 24 is connected to the left and right rear wheels RW1, RW2 via a rack and pinion mechanism 25, a relay rod 26, left and right tie rods 27a, 27b and left and right knuckle arms 28a, 28b,
The left and right rear wheels RW1 and RW2 are steered according to the rotation of the coaxial shaft 24. A control valve 31 is attached to an intermediate portion of the steering shaft 24, and the valve 31 powers the hydraulic oil discharged by the hydraulic pump 32 and supplied through the conduit P3 according to the steering torque acting on the steering shaft 24. The oil is supplied to one oil chamber of the cylinder 33, and the hydraulic oil from the other oil chamber of the cylinder 33 is discharged to the reservoir 22 via the conduit P4. The power cylinder 33 assists the steering of the left and right rear wheels RW1 and RW2 by axially driving the relay rod 26 according to the supply and discharge of the hydraulic oil. The electric control unit C includes a front wheel steering angle sensor 41 and a vehicle speed sensor 4
2. It has a yaw rate sensor 43 and a rear wheel steering angle sensor 44. The front wheel steering angle sensor 41 detects the steering angles δf of the left and right front wheels FW1 and FW2 from the rotation angle of the steering shaft 12 from the reference position,
A front wheel steering angle signal that indicates the detected front wheel steering angle δf is output. The vehicle speed sensor 42 detects the vehicle speed V based on the rotation speed of a transmission (not shown), and outputs a vehicle speed signal indicating the detected vehicle speed V. The yaw rate sensor 43 detects the yaw rate γ based on the rotation speed in the horizontal plane of the vehicle body and detects the yaw rate γ.
Output a yaw rate signal. Rear wheel steering angle sensor 44
Detects the rear wheel steering angle δr based on the amount of displacement of the relay rod 26 from the reference position, and outputs a rear wheel steering angle signal representing the detected rear wheel steering angle δr. Note that the detected front wheel steering angle δf and the detected rear wheel steering angle δr are positive (or negative) depending on the left and right front wheels FW1,
FW2 and the left and right rear wheels RW1 and RW2 represent steering angles to the right (or left) respectively, and the detected yaw rate γ represents a yaw rate generated when the vehicle turns right (left turn) by positive (or negative). . Detection output signals from these sensors 41 to 44 are supplied to the microcomputer 45. The microcomputer 45 comprises a ROM 45b, a CPU 45c, a RAM 45d and an I / O (input / output interface) 45e which are connected to the bus 45a. ROM45b is a program corresponding to the flowchart of FIG. 3, and a reference steering angle coefficient Kδ ₀ that changes according to the vehicle speed V, a corrected steering angle coefficient Kδ ₁ , a reference yaw rate coefficient Kγ _0, and a correction as shown in the graph of FIG. The yaw rate coefficient Kγ ₁ is stored. The reference steering angle coefficient Kδ ₀ and the reference yaw rate coefficient Kγ ₀ are for calculating the target rear wheel steering angle according to the front wheel steering angle and the yaw rate, and are theoretically and optimally determined in advance for each vehicle by a feeling evaluation. ing. The corrected steering angle coefficient Kδ ₁ is for calculating the optimum target rear wheel steering angle only by the front wheel steering angle, and the reference steering angle coefficient Kδ ₀ is added to the reference yaw rate coefficient K.
It is predetermined in consideration of γ ₀ . The corrected yaw rate coefficient Kγ ₁ is for calculating the optimum target rear wheel steering angle only by the yaw rate, and is determined in advance by considering the reference yaw rate coefficient Kγ ₀ and the reference steering angle coefficient Kδ ₀ . CP
The U 45c starts execution of the program in response to the closing of an ignition switch (not shown), and the RAM 45d temporarily stores variable data necessary for executing the program. The I / O 45e has a built-in circuit such as a memory circuit, an A / D converter, a D / A converter, etc. for exchanging signals with an external circuit, and is connected to various sensors 41 to 44. A warning lamp 46 and a drive circuit 47 are connected to this I / O 45. The warning lamp 46 is provided on the front panel in the vehicle compartment, and is lit to warn the driver of abnormality of the front wheel steering angle sensor 41 and the yaw rate sensor 43. The drive circuit 47 controls the rotation of the electric motor 23. The drive circuit 47 controls the electric motor 23 to the right by a positive rear wheel steering control signal supplied from the microcomputer 45, and also controls the electric motor 23 by a negative rear wheel steering control signal. Controls 23 to the left. Next, the operation of the embodiment configured as described above will be described. When the steering wheel 11 is rotated rightward or leftward while the vehicle is traveling, the rotation is transmitted to the relay rod 14 via the steering shaft 12 and the rack and pinion mechanism 13,
14 is displaced in the axial direction according to the rotation of the steering handle 11 while being assisted by the power cylinder 21. And, the axial displacement of the relay rod 14 is caused by the left and right tie rods 15a,
Left and right front wheel FW via 15b and left and right knuckle arms 16a, 16b
The front wheels FW1 and FW2 are transmitted to 1 and FW2, and the front wheels FW1 and FW2 are steered to the right or left, and the vehicle starts turning to the right or to the left. On the other hand, at this time, the CPU 45c starts the execution of the program in step 50, initializes the new front wheel steering angle data δf _N and the new yaw rate data γ _N to “0” in step 51, and then executes step 52- The circulation process consisting of 66 is repeatedly executed to control the steering of the left and right rear wheels RW1, RW2. In addition,
The new front wheel steering angle data δf _N and the new yaw rate data γ _N represent the current front wheel steering angle δf and yaw rate γ detected by the front wheel steering angle sensor 41 and the yaw rate γ, respectively. Data δ f ₀
And the old yaw rate data γ ₀ respectively represent the past front wheel steering angle δf and the yaw rate γ detected by the front wheel steering angle sensor 41 and the yaw rate sensor 43 before one cycle of the circulation processing. In this circulation process, the vehicle speed sensor is detected in step 52.
The vehicle speed signal from 42 is read and set as vehicle speed data V, and at step 53 the rear wheel steering angle sensor 44
The rear wheel steering angle signal is read and set as the rear wheel steering angle data δr. Next, in step 54, the old front wheel steering angle data δf ₀ is updated by the new front wheel steering angle data δf _N , and in step 55 the front wheel steering angle signal from the front wheel steering angle sensor 41 is read and the new front wheel steering is performed. Angle data δ
f _N , the old yaw rate data γ ₀ is updated by the new yaw rate data γ _N in step 56, and the yaw rate signal from the yaw rate sensor 43 is read in step 57 and set as the new yaw rate data γ _N. It After setting the various data V, δr, δf ₀ , δf _N , γ ₀ , γ _N , in steps 58 to 60, an abnormality determination of the front wheel steering angle sensor 41 and the yaw rate sensor 43 is made, for example, based on the following conditions. . A. Front-wheel steering angle sensor 41 (step 58) If the new front-wheel steering angle data δf _N indicates a value that is impossible for the vehicle traveling in light of the vehicle speed data V and the new yaw rate data γ _N , the front-wheel steering angle is calculated. It is determined that the sensor 41 has an abnormality. When the difference between the new front wheel steering angle data δf _N and the old front wheel steering angle data δf ₀ indicates a value that is impossible for vehicle traveling,
It is determined that the front wheel steering angle sensor 41 is abnormal. B. Yaw rate sensor 43 (steps 59, 60) When the new yaw rate data γ _N indicates a value that is impossible for the vehicle running, in light of the vehicle speed data V and the new front wheel steering angle data δf _N , the yaw rate sensor 43 It is determined that an abnormality has occurred in the. If the difference between the new yaw rate data γ _N and the old yaw rate data γ ₀ indicates a value that is impossible for vehicle traveling,
It is determined that the yaw rate sensor 43 has an abnormality. In this case, if there is no abnormality in the front wheel steering angle sensor 41 and the yaw rate sensor 43, it is determined as "NO" in both steps 58 and 59, and in step 61, the new front wheel steering angle data δf _N and new The reference steering angle coefficient Kδ ₀ read from the ROM 45b according to the yaw rate data γ _N and the vehicle speed data V
Based on the reference yaw rate coefficient Kγ ₀ and the calculation of the following equation 1, the target rear wheel steering angle δr * is determined, and in step 66, the determined target rear wheel steering angle δr * and the rear wheel steering angle δr are calculated. The rear wheel steering control signal δr * −δr representing the difference between the two is output to the drive circuit 47. δr * = Kδ ₀ · δf _N + Kγ ₀ · γ _N ... Formula 1 The drive circuit 47 supplies the rear wheel steering control signal δr * -δr.
Since the rotation of the electric motor 23 is controlled according to the
Rotates by an amount corresponding to the control signal δr * −δr. The rotation of the steering shaft 24 is caused by the rack and pinion mechanism 25.
Is transmitted to the relay rod 26 via the, and the rod 26 is displaced in the axial direction according to the rotation while being assisted by the power cylinder 33. The axial displacement of the relay rod 26 is transmitted to the left and right rear wheels RW1, RW2 via the left and right tie rods 27a, 27b and the left and right knuckle arms 28a, 28b, and the rear wheels RW1, RW2 are controlled by the rear wheel steering control. The steering is performed according to the signal δr * −δr. In such a case, the rear wheel steering control signal δr *
Since −δr represents the difference between the target rear wheel steering angle δr * and the current steering angles δr of the left and right rear wheels RW1, RW2, the rear wheels RW1, RW2 are feedback-controlled to the target rear wheel steering angle δr *. Will be steered. Accordingly, when both the front wheel steering angle sensor 41 and the yaw rate sensor 43 are normal, the left and right rear wheels RW1 and RW2 are steering-controlled according to the front wheel steering angle δf and the yaw rate γ as the vehicle turns, The maneuverability during turning of the vehicle is extremely good. If an abnormality occurs in the yaw rate sensor 43 and only the front wheel steering angle sensor 41 is normal, the step 5
It is determined to be “NO” and “YES” at 8 and 59, respectively, and at step 62, the new front wheel steering angle data δf _N and the corrected steering angle coefficient Kδ ₁ read from the ROM 45b according to the vehicle speed data V. Based on the above, the calculation of the following equation 2 is executed, and the target rear wheel steering angle δ
r * is determined, and the left and right rear wheels RW1, RW2 are steered to the determined target rear wheel steering angle δr * as described above. δr * = Kδ ₁ · δf _{N (} Equation 2) In such a case, the corrected steering angle coefficient Kδ ₁ is a reference for calculating the optimum target rear wheel steering angle δr * only by the front wheel steering angle δf, as described above. Since the reference yaw rate coefficient Kγ ₀ is added to the rudder angle coefficient Kδ ₀ in advance, even if an abnormality occurs in the yaw rate sensor 43, the steerability during turning of the vehicle depends on the detected front wheel steering angle δf. And keeps good. If an abnormality occurs in the front wheel steering angle sensor 41 and only the yaw rate sensor 43 is normal, steps 58, 60
Are judged as “YES” and “NO” respectively in step 63.
Then, based on the new yaw rate data γ _N and the corrected yaw rate coefficient K γ ₁ read from the ROM 45b according to the vehicle speed data V, the calculation of the following equation 3 is executed to determine the target rear wheel steering angle δr *. , Left and right rear wheels RW1, RW2 as described above
Is controlled to the determined target rear wheel steering angle δr *. δr * = Kγ ₁ · γ _{N (} Equation 3) In such a case, the corrected yaw rate coefficient Kγ ₁ is, as described above, the optimum target rear wheel steering angle δr based on the yaw rate alone.
Since the reference yaw rate coefficient Kγ ₀ is added to the reference steering angle coefficient Kδ ₀ in order to calculate *, even if an abnormality occurs in the front wheel steering angle sensor 41, the steering operation during turning of the vehicle is suppressed. The goodness is maintained depending on the detected yaw rate γ. If an abnormality occurs in both the front wheel steering angle sensor 41 and the yaw rate sensor 43, both are determined as “YES” in steps 58 and 60, and the target rear wheel steering angle δ is determined in step 64.
r * is determined to be a fixed value irrelevant to the new front wheel steering angle data δf _N and the new yaw rate data γ _N , for example, “0”, and the left and right rear wheels RW1 and RW2 are the determined target rear wheel steering angle δ as described above.
The steering is controlled to r * (= 0). As a result, the left and right rear wheels RW
For the steering control of 1 and RW2, the detection results of the front wheel steering angle sensor 41 and the yaw rate sensor 43, which are both abnormal, are not used. Will be optimal. As can be understood from the description of the operation, according to the above-described embodiment, the front wheel steering angle sensor 41 or the yaw rate sensor is used.
When an abnormality occurs in 43, the target rear wheel steering angle δr * is determined to a value in consideration of the undetectable front wheel steering angle δf or yaw rate γ according to the combination of the abnormality occurrence states of the sensors 41, 43. At the same time, the left and right rear wheels RW1 and RW2 are steered to the determined target rear wheel steering angle δr *.
Even if any of the abnormalities 1 and 43 occurs, the vehicle maneuverability is maintained at the best in each abnormal state. Further, as described above, when an abnormality occurs in the front wheel steering angle sensor 41 or the yaw rate sensor 43, the lighting control signal is output to the warning lamp 46 in step 65 after the processing in steps 62 to 64. It This allows the warning lamp
Since 46 lights up, the abnormality of each of the sensors 41 and 43 is visually recognized by the driver, and the same person can deal with the abnormality.

[Brief description of drawings]

FIG. 1 is a claim correspondence diagram corresponding to the configuration of the present invention, and FIG.
FIG. 1 is an overall schematic view of a front and rear wheel steering vehicle showing an embodiment of the present invention, FIG. 3 is a flowchart corresponding to a program executed by the microcomputer of FIG. 2, and FIG. 4 is a microcomputer of FIG. 5 is a change characteristic graph of a steering angle coefficient and a yaw rate coefficient used for determining a target rear wheel steering angle in FIG. Explanation of symbols A ... front wheel steering mechanism, B ... rear wheel steering mechanism, C ... electric control device, FW1, FW2 ... front wheels, RW1, RW2 ... rear wheels, 11 ...
Steering wheel, 14,26 …… Relay rod, 23 …… Electric motor, 41 …… Front wheel steering angle sensor, 42 …… Vehicle speed sensor, 43
…… Yaw rate sensor, 44 …… Rear wheel steering angle sensor, 45…
… Microcomputer.

Claims (1)

(57) [Claims] 1. A rear wheel steering mechanism for steering a rear wheel, a front wheel steering angle detecting means for detecting a front wheel steering angle, a yaw rate detecting means for detecting a yaw rate, and a target based on the detected front wheel steering angle and the detected yaw rate. An electric control device for determining a rear wheel steering angle and electrically controlling the rear wheel steering mechanism to steer the rear wheels to the target rear wheel steering angle. In the electric control device, the abnormality detection means for detecting an abnormality in the front wheel steering angle detection means, and the detected front wheel steering angle and the detected yaw rate when the abnormality detection means detects no abnormality in the front wheel steering angle detection means Based on the above, the sum of the front wheel steering angle control component that increases as the front wheel steering angle increases and the yaw rate control component that increases as the yaw rate increases is determined as the target rear wheel steering angle. The first target rear wheel steering angle determining means and the abnormality detecting means when the abnormality of the front wheel steering angle detecting means is detected, the yaw rate control component is corresponded to the front wheel steering angle control component based on the detected yaw rate. Second target rear-wheel steering angle determining means for determining the target rear-wheel steering angle with the corrected amount taken into consideration, and a control signal corresponding to the determined target rear-wheel steering angle is output to the rear-wheel steering mechanism. A rear wheel steering control device for a front and rear wheel steering vehicle, comprising: a control signal output means for controlling the rear wheels to be set to the determined target rear wheel steering angle.